Just notcied there is writing on the tube screen behind but not on the  contract screen. the light was just right to see the "13T"

Anyone seen this on their MX models? 

Hi,

It looks like someone at some point has physically handwritten it on the tube face and didn't clean it properly prior to reassembly. The contrast screen can be removed to clean it if desired. If I recall correctly you can unclip the two plastic strips above and below the contrast screen to gain access to the screws.

Steve

EDIT: I see that the thread title say's MX5000 and the picture say's MX4000. If it's the MX4000 with a plastic contrast screen it can be popped out from the bottom without the need to remove any screws.

that makes sense.  Thank you for the disassembly tips as well. 

It is a US MX5000 not 4000 as my images state. 

Must be the glass contrast screen type as Stonk first mentioned then.

The plastic strips will be difficult to remove unless you know the correct way. Push the end of the strip from the front of the set towards the rear - it should go in a few millimeters, and you can then pry the end of the strip outwards from the side of the set. It should then clear off the fixing clip when you let go from the front.

Repeat for the three remaining ends and you should be able to carefully remove the strips. Be careful with the lower one so you don't tear the speaker cloth.

The glass is HEAVY! Have an extra pair of hands to help, or at least a mattress or something in front of the set in case it slips from your hands.

Above instruction works for an MX5000/5500/6000/7000. If it is an MX4000 with a glass contrast screen you will not habe to remove the plastic parts above and below the screen. In this case the backcover has to be removed. After this one of the sidepanels which hold the screen in place can be removed. Be carefull, when the sidepanel is removed the screen will fall off, so have someone hold the screen when you remove the sidepanel. 

Regarding the problem, does the tekst seem to be on or behind the glass of the picturetube? This could be a logo of a TV station which is burned into the screen (yes, this also happens to picturetubes, not just plasma!) and there is no way of getting this out. Good luck!